While Oliver is gutting it out in the Wild, Wild West, Susan is living the high-society life on the East Coast. By now, she's begun getting paid to work as an artist.
Susan continues to write letters to Oliver, but she has her sights set on someone else at the moment: Thomas Hudson. Thomas is a literary editor and best bro to Susan and Augusta.
Susan loves Thomas because he is a pure fancy pants, a smart and sensitive man who we'll learn is also the "greatest editor" in the country (1.3.15). Even our knees are getting weak now.
After a few years, Susan realizes that Thomas is actually in love with Augusta. Bummer. Although this breaks Susan's heart (and leads her to write a nasty letter to her BFF), she eventually makes peace with her best friends' relationship.
And then, there's this: just two days after Susan learns about this love affair, she receives a letter from Oliver saying that he's coming back to the East Coast.
Susan picks up Oliver from the train station. He's acting pretty Clint Eastwood-y at this point: when he arrives at her house, he makes a big show of placing his tobacco pipe and great woodenhandled revolver on her dresser.